Spreading Fire with Expressions

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Old 03 March 2013   #1
Spreading Fire with Expressions

Hi,
I am currently making a tool for my Final Major Project that takes an object in Maya, and spreads fire through said object using Maya fluids. I am currently looking into using emission ramps driven by expressions to spread through the object. What I need to know is, is there a way to drive the ramp without using the likes of time or frame?

The current expression I have driving the spread is:
float $speed = 0.25;
ramp2.colorEntryList[0].position = time*$speed;

This moves the colour on the ramp up until it is full. The problem here is that the spread is based on the current time and may start burning half way through the object. Is there any way of gradually increasing the position without using time or frame, so the fire can start, at for argument sake frame 50.

This might be a trivial question with a stupidly simple answer, but I feel I've stared at it for too long and need some outside input.

Also, if anyone has any better methods to spread fire in Maya I would gladly receive them!

Any help if greatly appreciated!
 
Old 03 March 2013   #2
Generally you want to access the variable time at some point in an animating expression, if only to reset your own variables on rewind. I think the simplest thing to do if you want the effect to start at frame 50 is to use an if statement:

float $speed = 0.25;
float $t=0;
float $startFrame = 50;

if( time > $startFrame )
$t = time-$startFrame;

ramp2.colorEntryList[0].position = $t*$speed;


Duncan
 
Old 03 March 2013   #3
Thank you for the reply. I figured something similar in the end, guess I just needed to take a step back, do something else then go back to it! I am currently working on python functions being called with expressions overall making it easier for me to understand work with.

I was wondering if you could possibly help with my latest question:
Constant fluid integrity over varying Voxel Counts Constant fluid size over varying voxel counts

Thanks again, the help was appreciated.
 
Old 03 March 2013   #4
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